When a network in an area is congested, a service provided by an application server for user equipment (UE) in the area is affected. For example, a service transmission delay increases, service bearer establishment fails, and a transmission rate is limited. Because the application server cannot perceive a congestion status, the application server continues performing downlink data transmission, which causes a waste of a network resource and may lead to a failure to properly use some important services due to a poor network condition.